31 October 2014

Perspiration Power

Welcome back. A couple of years ago, I described a bio-battery that, if multiplied, I conjectured, could probably power your house (Snail Power). You didn’t jump on my idea, did you? OK, so maybe filling your basement with electrode-protruding snails, especially the illegal, giant African variety, wasn’t such a great idea.

Think smaller; and it’s not my idea. Recent studies by the University of California San Diego, with contributors from China’s Southeast University and India’s Central Electrochemical Research Institute, are heading toward a bio-battery that seems more like the Spray-on Batteries that I also described a couple years ago, even if those weren’t bio-batteries.

Papers on this new bio-battery have appeared in different journals, and a press release on the latest conference presentation was picked up by media much more alert than I. You too may be way ahead of me on this. Nevertheless, the findings are so intriguing, I’ll take that risk. How could I resist writing about a bio-battery that’s fueled by perspiration? Yes, sweat!

Bio-Batteries and Lactate Monitoring

Bio-batteries are like rechargeable cell batteries we can
buy for electronic devices, except they’re recharged by organic
compounds, most commonly glucose, a simple sugar.

Although there are numerous sources of glucose and many possible uses for bio-batteries, to power medical devices, such as heart pacemakers, it’s anticipated that implanted bio-batteries will tap into glucose in the bloodstream.

An alternative approach for powering biomedical devices or at least wearable electronic devices came with a noninvasive measurement of lactate, a breakdown product of glucose that’s in the blood but also excreted in perspiration.

In general, increased exercise intensity produces increased lactate. Monitoring lactate levels is regularly done in training of professional and elite athletes as well as for certain medical conditions. That measurement has required blood testing.

Step one of the new research was to develop a sensor to measure and monitor lactate in perspiration. The sensor has an enzyme that strips electrons from lactate to generate a weak electrical current. The investigators imprinted the sensor onto temporary tattoo paper, which, for testing, they stuck to the arms of ten volunteers. They monitored the electrical current while the volunteers rode stationary exercise bikes at increasing levels of resistance for 30 minutes.

Going further, the researchers designed a bio-battery from the tattoo sensor. The anode contained the enzyme that strips the electrons from lactate; the cathode contained a molecule that accepts the electrons. For testing, they applied the tattoo bio-batteries to 15 volunteers of different fitness levels and measured the bio-battery power the volunteers produced by riding a stationary bike for 30 minutes.

The least fit volunteers generated the most power since their level of exertion was greatest. Still, the power they generated was very low. Work continues on improving the power capacity and incorporating the bio-battery into headbands and wristbands.

There’s little doubt that advances in bio-batteries will benefit future biomedical devices and wearable electronics, and it’s likely that lactate-powered bio-batteries will play a role.

Wrap Up

As I was developing this blog post, I had to remind myself that high humidity alone will generate perspiration but probably not a lot of lactate for power. Maybe, instead of snails in the basement, you could just wrap kids in these new bio-batteries and let them run around. I’m sure that when our son was young, he could have powered our house; maybe the neighborhood. Thanks for stopping by.